Function swap_to_fixed_update

pub fn swap_to_fixed_update<A: Actionlike>(
    query: Query<'_, '_, &mut ActionState<A>>,
    action_state: Option<ResMut<'_, ActionState<A>>>,
)

We are about to enter the FixedMain schedule, so we:

• save all the changes applied to state into the update_state
• switch to loading the fixed_update_state